At seven test sites stems counts indicated reduction in plant densities by 50 percent or more.   Pictorial comparisons also support claims of 2006 success  (See examples elsewhere on the District’s web-site).

Note that it is not possible to completely eradicate Flowering Rush. The herbicide does not impact submerged plants, including young ones. Such plants can be expected to appear above the water surface in a subsequent year. Hence, it is anticipated that several years will be required to achieve a high degree of control.

After the 2006 treatment some areas did not appear to be helped. It is believed that these areas either inadvertently escaped treatment, or were disturbed shortly after treatment, possibly by boats or waves. 

The 2007 treatment program occurred about two weeks earlier than in 2006; this year’s earlier application was somewhat exaggerated from the plant’s perspective because of the plant’s somewhat delayed development in comparison to the previous year.      

The 2006 and 2007 treatments were authorized by the DNR after three years of testing on several sites on Big and Little Detroit, Deadshot Bay (Curfman), Melissa and Sallie. In 2006 and 2007 the chemical herbicide imazapyr (which is made available under the trademark Habitat) was applied to all homogeneous stands of emergent flowering rush.  

Treatment locations in 2007 were very similar to those in 2006 (See 2006 Executive Summary for map).  Nearly all of the treated sites on Sallie and Melissa are very small, often only a few isolated spears, but including clumps up to four feet in diameter. On Big, Little Detroit and Curfman the treatment areas are quite a bit larger, ranging in size from 6-foot clumps, to more than an acre.      

Treatments were carried out by Mr. Denton Offutt, a licensed herbicide applicator, from a specially adapted pontoon boat.   The Habitat (Imazapyr) was mixed with a surfactant to promote adhesion of the herbicide to the plant material. A sprayer boom was used for larger treatment areas; a high pressure sprayer was used on smaller stands and those in shallow water.   

Just under 33 gallons of Habitat concentrate were applied to about 87 acres on the five lake basins (74 acres on Big, Little Detroit, and Curfman). This year’s total cost was $58,000 down somewhat from last year because of carry-over stocks of chemical.   

The success of this year’s treatment program will be evaluated in June, 2008.

 prepared by Dick Hecock, August 2007

2007 Flowering Rush Comparisons
(click on title to download report)
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(click on title for a printable version)

Most of the 2006 treated sites were very small, rarely more than a few isolated spears, up to clumps that were four feet in diameter.  These smaller sites were mostly found on Melissa and Sallie.  The larger treatment sites were mainly found on Big, Little Detroit and Curfman.

Just under 37 gallons of Habitat concentrate were applied (together with a surfactant to promote adhesion of the herbicide to the plant),  to about 99 acres on the five lake basins (93 acres on Big, Little Detroit, and Curfman).  The total cost was $72,500 of which 75% was for labor.

Handwicking tests were continued on two near-shore sites on Big Detroit Lake,  in order to help ascertain the feasibility of small-scale applications.

prepared by Dick Hecock, September 2006  
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Pelican River Watershed District
2005 Flowering Rush Herbicide Tests

Chemical applications to several flowering rush test plots were performed during the last week of July and into the first week of August, 2005. This year’s testing program built on two previous years of testing at test sites on Big Detroit and Deadshot Bay (Curfman). This year’s effort was primarily focused on the chemical herbicide imazapyr (also known as Habitat) which had shown special promise after last year’s tests.